Generally, in a crawler dozer, for example, as disclosed in Patent Document 1, a vibration proofing mount apparatus is interposed at four positions comprising front, rear, right and left sides between a vehicle body frame and a floor portion of a cab frame. Further, the structure is made such that the vibration proofing mount apparatus damps and reduces vibrations and impact applied to the cab frame so as to improve the riding comfort.
In a work machine such as the crawler dozer or the like, in order to protect an operator even in the case that an excessive load is applied to the cab frame by a vehicle body weight in the case of rolling over or the like, it is important to set up a function of a roll-over protective structure (ROPS) with respect to the cab frame. In this case, since excessive load applied to the cab frame is concentrated on a portion corresponding to each of the vibration proofing mount apparatuses between the vehicle body frame and the cab frame, the portions are likely to be damaged. Accordingly, in conventional crawler dozers, limiting mechanisms for limiting a movement in a vertical direction, a front-rear direction and a lateral direction of the cab frame within a predetermined range are respectively provided between the floor portion of the cab frame and the vehicle body frame at four positions corresponding to the respective vibration proofing mount apparatuses, whereby it is possible to bear the excessive load applied to the cab frame by this limiting mechanism.
However, in the case that the limiting mechanisms for limiting the movement in all the directions comprising the vertical, front-rear and lateral directions are provided at four positions corresponding to the respective dampers, as in the conventional structure, there is a problem that the structure becomes complicated, and the manufacturing costs become high.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2002-138512